sRGB

sRGB was standardised by the IEC as Colour management, Default RGB colour space, sRGB, in IEC 61966-2-1. CSS Color 4 gives its primaries as red at x 0.640, y 0.330, green at 0.300, 0.600 and blue at 0.150, 0.060, with a D65 white point. It is the colour space a web page, an image without a profile and most documents are assumed to be in, so a colour written in ordinary CSS is an sRGB colour.

Being the default makes it the baseline for everything else. MDN describes a device matching the srgb value of the color-gamut media query as one that can show approximately the sRGB gamut or more, which includes the vast majority of colour displays. A wider panel shows sRGB content correctly only when the system knows the content is sRGB and maps it; without colour management, sRGB images look oversaturated on a wide-gamut screen.

Many monitors offer an sRGB mode that clamps a wide panel to the sRGB gamut on purpose, which is useful for accurate web and office work and narrows what a wide-gamut test can show. If the colour gamut test reports sRGB on a screen sold as wide gamut, check that mode, the colour profile the system uses for the screen, and on Windows whether automatic colour management is on.